Electric compressor

ABSTRACT

An electric motor that has a electric motor and a compression mechanism. The motor and the compression mechanism are accommodated in a single chamber. A single shaft functions as the output shaft of the motor and the drive shaft of the compressor.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to an electric compressor employed in, for example, air conditioners for vehicles.

[0002] In general, a compressor that is used in an air conditioner for a vehicle is driven by an engine. Recently, however, battery powered electric vehicles have been put to practical use. In these vehicles, the compressor is driven by an electric motor.

[0003] A typical refrigerant circuit of a heat exchanger such as a vehicle air conditioner includes a compressor such as an electric compressor. A typical electric compressor such as a compressor disclosed in Japanese Unexamined Patent Publication No. 5-187356 has an electric motor and a refrigerant compression mechanism, which are housed in a casing. The compression mechanism is driven by the motor and includes pistons and a swash plate. Each piston reciprocates in a corresponding cylinder bore. The swash plate converts rotation of the motor into reciprocation of each piston.

[0004] A chamber that accommodates the motor is separated from a chamber that accommodates the compression mechanism by a wall. Since the output shaft of the motor also serves as the drive shaft of the compression mechanism, the drive shaft extends through the separation wall and protrudes into the compression mechanism chamber. Therefore, the compression mechanism and the motor are spaced apart by a relatively great distance in the axial direction of the drive shaft, which increases the size of the compressor. In a vehicle, especially in a passenger car, a compressor preferably occupies minimal space.

BRIEF SUMMARY OF THE INVENTION

[0005] Accordingly, it is an objective of the present invention to provide a compact electric compressor that is easy to install and occupies minimal space when used in the air conditioner of a passenger car.

[0006] To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, an electric compressor that has an electric motor and a compression mechanism is provided. The motor and the compression mechanism are accommodated in a housing. The compressor includes a chamber for accommodating the electric motor and the compression mechanism and a shaft that functions as the output shaft of the motor and the drive shaft of the compression mechanism.

[0007] Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

[0009]FIG. 1 is a cross-sectional view illustrating a compressor according to a first embodiment of the present invention; and

[0010]FIG. 2 is a cross-sectional view illustrating a compressor according to a second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] A variable displacement electric compressor 1 according to a first embodiment of the present invention will now be described with reference to FIG. 1.

[0012] As shown in FIG. 1, the compressor 1 includes a cylinder block 2, a front housing member 3, which is secured to the front end face of the cylinder block 2, and a rear housing member 5, which is secured to the rear end face of the cylinder block 2. A valve plate assembly 4 is located between the cylinder block 2 and the rear housing member 5. The housing members 3, 5 and the cylinder block 2 are secured to one another by bolts (not shown).

[0013] The cylinder block 2 and the front housing member 3 define a crank chamber 6. A compression mechanism 7 and an electric motor 8, which drives the compression mechanism 7, are accommodated in the crank chamber 6. A drive shaft 9 of the compression mechanism 7 extends between the front housing member 3 and the cylinder block 2. The drive shaft 9 also functions as the output shaft of the motor 8. The drive shaft 9 is supported by radial bearings 10. The front end of the drive shaft 9 contacts a thrust bearing 11. The rear end of the drive shaft 9 contacts a spring 12, which is located in a recess formed in the center of the cylinder block 2. The spring 12 urges the drive shaft 9 forward.

[0014] The motor 8 includes a stator 13, which is fixed to the front housing member 3, and a rotor 14, which is fixed to and rotates integrally with the drive shaft 9. The rotor 14 has silicon steel sheets 15 has a number of laminated silicon steel sheets 15. An end plate (rotor end) 16 is located at each axial end of the rotor 14 to prevent the steel sheets 15 from moving axially. The end plates 16 are made of nonmagnetic material such as aluminum, stainless steel and brass.

[0015] A lug plate 17, a cam plate, which is a swash plate 18 in this embodiment, and a hinge mechanism 19 are attached to the drive shaft 9. The hinge mechanism 19 is located between the lug plate 17 and the swash plate 18. The lug plate 17 is integrally formed with the rear end plate 16. That is, one of the rotor ends of the rotor 14 is integrally formed with the rotation portion of the compression mechanism. Also, the front end plate 16 is fixed to the drive shaft 9 by a snap ring (not shown).

[0016] The swash plate 18 is supported on the drive shaft 9. The lug plate 17 and the hinge mechanism 19 permit the swash plate 18 to slide along the drive shaft 9 and incline with respect to the axis of the drive shaft 9. The lug plate 17 and the hinge mechanism 19 drive the swash plate 18 to rotate integrally with the drive shaft 9.

[0017] Cylinder bores 2 a (only one is shown) are formed in the cylinder block 2. The bores 2 a are arranged at equal angular intervals about the drive shaft 9. Each cylinder bore 2 a extends parallel to the drive shaft 9 and reciprocally accommodates a single-headed piston 20. The front portion of each piston 20 is coupled to the swash plate 18 by a pair of shoes 21. A compression chamber 22 is defined in each cylinder bore 2 a between the end face of the associated piston 20 and the valve plate assembly 4. The volume of each compression chamber 22 changes in accordance with reciprocation of the associated piston 20.

[0018] A suction chamber 23 and an annular discharge chamber 24 are defined in the rear housing member 5. The discharge chamber 24 surrounds the suction chamber 23. The valve plate assembly 4 has suction ports 25 and discharge ports 26. Each suction ports 25 and each discharge ports 26 correspond to one of the compression chambers 22. Suction valves flaps 25 a and discharge valve flaps 26 a are formed on the valve plate assembly 4. Each suction valve flap 25 a corresponds to one of the suction ports 25 and each discharge valve flap 26 a corresponds to one of the discharge ports 26.

[0019] A supply passage 27 and a bleed passage 28 are formed in the cylinder block 2, the valve plate assembly 4 and the rear housing member 5. The supply passage 27 connects the crank chamber 6 with the discharge chamber 24. The bleed passage 28 connects the crank chamber 6 with the suction chamber 23. The supply passage 27 is provided with a control valve 29. The control valve 29 may have the same structure, for example, as the control valve disclosed in Japanese Unexamined Patent Publication 6-123281 and includes a diaphragm and a valve mechanism (neither is shown). The diaphragm is displaced in accordance with the pressure in the suction chamber 23. The valve mechanism adjusts the opening size of the supply passage 27 according to the pressure in the suction chamber 23.

[0020] When the pressure in the suction chamber 23 falls below a predetermined level, the control valve 29 opens the supply passage 27. When the pressure in the suction chamber 23 is equal to or higher than the predetermined level, the control valve 29 closes the supply passage 27. In this manner, the control valve 29 controls the pressure in the crank chamber 6, which adjusts the displacement of the compressor 1.

[0021] The operation of the compressor 1 will now be described.

[0022] When the motor 8 rotates the drive shaft 9, the swash plate 18 rotates integrally with the drive shaft 9. Rotation of the swash plate 18 is converted into reciprocation of each piston 20 by the corresponding shoes 21. Accordingly, suction, compression and discharge of refrigerant are repeated in each compression chamber 22. Refrigerant drawn into the suction chamber 23 from an external refrigerant circuit is drawn into each compression chamber 22 through the corresponding suction port 25. The refrigerant in the compression chamber 22 is then compressed by the associated piston 20 and subsequently discharged to the discharge chamber 24 through the corresponding discharge port 26. Refrigerant discharged to the discharge chamber 24 is sent to the external refrigerant circuit through an outlet.

[0023] When the pressure in the suction chamber 23 is relatively low, the opening size of the control valve 29 is increased to raise the pressure Pc in the crank chamber 6, which decreases the inclination angle of the swash plate 18, or the angle defined by the swash plate 18 and an imaginary plane perpendicular to the drive shaft 9. Accordingly, the stroke of each piston 20 is decreased. As a result, the compressor displacement is decreased. When the pressure in the suction chamber 23 is relatively high, the opening size of the control valve 29 is decreased to lower the crank chamber pressure Pc, which increases the inclination angle of the swash plate 18. Accordingly, the stroke of each piston 20 is increased. As a result, the compressor displacement is increased.

[0024] When the drive shaft 9 is rotating, the rotor 14 receives a thrust force from the lug plate 17 due to the compression reaction force of the pistons 20. Since the snap ring (not shown) prevents the front end plate 16 from moving axially relative to the drive shaft 9, the silicon steel sheets 15 are held between the front end plate 16 and the lug plate 17 and are not displaced from the predetermined locations even if the speed of the drive shaft 9 is high.

[0025] The embodiment of FIG. 1 has the following advantages.

[0026] (1) The motor 8 and the compression mechanism 7 are accommodated in the same crank chamber 6. Thus, the compressor does not need to have two chambers and a partition, and the motor 8 and the compression mechanism 7 may be arranged as close to each other as possible. This structure reduces the size and weight of the compressor 1.

[0027] (2) The lug plate 17 fixes the silicon steel sheets 15 of the rotor 14 are fixed on the drive shaft 9, which further reduces the axial size of the compressor 1.

[0028] (3) One of the rotor ends 16 of the rotor 14 is integral with the lug plate 17, which reduces the number of parts and simplifies the assembly of the compressor 1.

[0029] (4) The compression mechanism 7 is a variable displacement type. Therefore, the compressor displacement of refrigerant per unit time is arbitrarily controlled in a wide range by controlling the speed of the drive shaft 9 of the motor 8 and by adjusting the displacement through the compression mechanism 7. In other words, the compressor displacement is effectively controlled.

[0030] A second embodiment of the present invention will now be described with reference to FIG. 2. Like or the same reference numerals are given to those components that are like or the same as the corresponding components of the embodiment of FIG. 1. A fixed displacement compressor 1 of FIG. 2 has a compression mechanism 7 that is greatly different from the compression mechanism 7 of the compressor 1 shown in FIG. 1. Specifically, the compression mechanism 7 of FIG. 2 has an annular swash plate 33 the inclination angle of which is fixed relative to the drive shaft 9. Rotation of the drive shaft 9 is converted into reciprocation of each piston 20 by the swash plate 33.

[0031] The rear end plate 16 of the rotor 14 is integrated with a cam member 30, which rotates integrally with the drive shaft 9. The cam member 30 includes a support surface 30 a and a boss 30 b. The support surface 30 a is inclined relative to the drive shaft 9 by a predetermined angle. The boss 30 b is perpendicular to the support surface 30 a. The swash plate 33 is rotatably supported by the cam member 30. A thrust bearing 31 is located between the swash plate 33 and the support surface 30 a. A radial bearing 32 is located between the swash plate 33 and the boss 30 b. In this embodiment, the discharge chamber 24 is radially inside the suction chamber 23. In other words, the suction chamber 23, which has a substantially annular shape, surrounds the discharge chamber 24.

[0032] When the drive shaft 9 is rotated by the motor 8, the cam member 30 rotates integrally with the drive shaft 9. At this time, the swash plate 33 contacts the support surface 30 a through the thrust bearing 31. Rotation of the cam member 30 reciprocates each piston 20 by a predetermined stroke, which corresponds to the inclination angle of the support surface 30 a. Accordingly, suction, compression and discharge of refrigerant are repeated in each compression chamber 22.

[0033] Therefore, in addition to the advantage (1) of the first embodiment, the second embodiment has the following advantages.

[0034] (5) The cam member 30 fixes the silicon steel sheets 15 on the drive shaft 9, which reduces the axial size of the compressor 1.

[0035] (6) The rear rotor end 16 of the rotor 14 is integral with the cam member 30, which reduces the number of parts and simplifies the assembly of the compressor 1.

[0036] (7) Compared to a variable displacement type compression mechanism, the compression mechanism 7 has a simpler structure.

[0037] (8) The swash plate 33 reciprocates the pistons 20 without rotating integrally with the drive shaft 9. Therefore, compared to a case where a swash plate rotates integrally with the drive shaft 9, there is less friction between the shoes 21 and the swash plate 33, which reduces noise and vibration.

[0038] (9) The swash plate 33 is supported on the cam member 30 through the roller bearing so that the swash plate 33 rotates relative to the cam member 30, which reduces friction between the cam member 30 and the swash plate 33. Accordingly, the life of the compressor 1 is extended.

[0039] It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the invention may be embodied in the following forms.

[0040] In the illustrated embodiments, the rear end plate 16 is integrated with the lug plate 17 or the cam member 30. However, the rear end plate 16 may be formed separately from the lug plate 17 or the cam member 30. Like in the illustrated embodiment, the lug plate 17 and the cam member 30 can be used to fix the silicon steel sheets 15. The lug plate 17 and the cam member 30 may be made of a material other than a nonmagnetic material.

[0041] A thrust bearing may be located between the front end plate 16 and the front housing member 3. In this case, compression reaction force that is applied to the lug plate 17 from the pistons 20 is received by the front housing member 3 through a relatively large area. Compared to the small thrust bearing 11, which supports the drive shaft 9 and receives compression reaction force, the thrust bearing located between the front end plate 16 and the front housing member 3 has an improved durability and permits the drive shaft 9 to rotate smoothly.

[0042] The stator 13 may radially overlap the reciprocation range of the pistons 20. Specifically, the front housing member 3 may be formed to have a greater diameter than the cylinder block 2, and the rear coil end of the stator 13 may located radially outside of the front end of the piston reciprocation range such that the rear coil end does not interfere with the pistons 20. This structure further reduces the axial size of the compressor 1.

[0043] The present invention may be applied to a wobble type compression mechanism, which has a wobble plate. The wobble plate changes its inclination angle without rotating integrally with the drive shaft 9.

[0044] The cam member may be integrally formed with the drive shaft 9.

[0045] The present invention may be applied to a compressor in which pistons are reciprocated by a predetermined stroke and a swash plate rotates integrally with a drive shaft 9.

[0046] In the illustrated embodiments, rotation of the drive shaft 9 is converted into reciprocation of the pistons 20 through the swash plate 18 or 33 and the shoes. However, the present invention may be applied to a vane compressor.

[0047] The control valve 29 may be replaced by an externally controlled valve the opening size of which is controlled by electric signals supplied from the outside.

[0048] The present invention may be applied to a multistage compressor. A multistage compressor includes a low pressure compression chamber and a high pressure compression chamber. Refrigerant is drawn into the low pressure compression chamber from an external refrigerant circuit and is compressed to an intermediate pressure. Refrigerant is then compressed again in the high pressure compression chamber.

[0049] In the illustrated embodiment, the present invention is applied to compressors in vehicle air conditioners. However, the present invention may be applied to a compressor in other types of refrigerant circuits.

[0050] In the illustrated embodiments, the present invention is applied to a compressor 1, which has single headed pistons 20. However, the present invention may be applied to compressors that have double headed pistons.

[0051] The refrigerant in the compressors 1 is not limited to a chlorofluorocarbon. For example, carbon dioxide (CO₂) may be used as refrigerant.

[0052] In the illustrated embodiments, the rotor 14 of the motor 8 is surrounded by the stator 13. In other words, the rotor 4 and the stator 13 are arranged in the radial direction of the drive shaft 9 and face each other. However, the present invention may be applied to an electric compressor that has an axial type motor. In an axial type motor, a rotor and a stator are arranged along the axial direction and face each other.

[0053] Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims. 

1. An electric compressor that has an electric motor and a compression mechanism, which are accommodated in a housing, the compressor comprising: a chamber for accommodating the electric motor and the compression mechanism; and a shaft that functions as the output shaft of the motor and the drive shaft of the compression mechanism.
 2. The electric compressor according to claim 1 , wherein the electric motor includes a rotor, wherein the rotor has an iron core that is formed by laminating a plurality of steel sheets and a pair of rotor ends, and wherein the rotor ends are located at the ends of the iron core to fix the core relative to the shaft.
 3. The electric compressor according to claim 2 , wherein the compression mechanism includes a rotating member that rotates integrally with the shaft, and wherein the rotating member is integrally formed with one of the rotor ends.
 4. The electric compressor according to claim 2 , wherein the compression mechanism includes: a cylinder bore formed in the housing; a piston that reciprocates in the cylinder bore; and a cam plate that can slide on and incline relative to the shaft, wherein the cam late is coupled to the piston and to the rotating member, wherein the cam plate converts rotation of the shaft into reciprocation of the piston, and wherein the inclination angle of the cam plate is adjusted to change the stroke of the piston.
 5. The electric compressor according to claim 2 , wherein the compression mechanism includes: a cylinder bore formed in the housing; a piston that reciprocates in the cylinder bore; and a swash plate that is supported on the shaft such that the inclination angle relative to the shaft is fixed, and wherein the swash plate converts rotation of the shaft into reciprocation by a constant stroke of the piston.
 6. The electric compressor according to claim 5 , wherein the rotating member includes a support surface that is inclined by a predetermined angle relative to the axis of the shaft and a boss that is perpendicular to the support surface, the compressor further comprising: a thrust bearing that is located between the swash plate and the support surface; and a roller bearing that is located between the swash plate and the boss, wherein the roller bearing permits the swash plate to rotate relative to the shaft.
 7. An electric compressor that has an electric motor and a compression mechanism, which are accommodated in a housing, the compressor comprising: a chamber for accommodating the electric motor and the compression mechanism; a shaft that functions as the output shaft of the motor and the drive shaft of the compression mechanism; wherein the compression mechanism includes: a rotating member that rotates integrally with the shaft; a plurality of cylinder bores formed in the housing; a plurality of pistons, wherein each piston can reciprocate in one of the cylinder bores; a cam plate that can slide on and incline relative to the shaft, wherein the cam late is coupled to the pistons and to the rotating member, wherein the cam plate converts rotation of the shaft into reciprocation of each piston, and wherein the inclination angle of the cam plate is adjusted to change the stroke of each piston; and wherein the electric motor includes a rotor, wherein the rotor has an iron core that is formed by laminating a plurality of steel sheets and a pair of rotor ends, and wherein the rotor ends are located at the ends of the iron core to fix the core relative to the shaft.
 8. The electric compressor according to claim 7 , wherein the compression mechanism includes a rotating member that rotates integrally with the shaft, and wherein the rotating member is integrally formed with one of the rotor ends. 